Benjamin was my great grandfather. I have done a great deal of research on Lyman (very fascinating man!) Would be happy to share what I have.
You mentioned Lyman's interest in the family and surveys he did. I read something about this in an article years ago that he wanted to submit the information for a study, but I'd never been able to locate any other reference.
You said, "they are interesting to read" Does that mean you've read them? Do you have copies or know where I could obtain them?? Its highly unusual for 15 children to not only survive, but from what I've been able to ascertain, all of them were SUCCESSFUL as well.